This proposal is a plan for carrying out a multicenter randomized clinical trial, designed to assess the efficacy of argon laser trabeculoplasty as an alternative to standard medical therapy of open angle glaucoma. The trial will involve the recruitment of 240 patients with newly diagnosed symmetrical open-angle glaucoma. Patients over the age of 30 years with intraocular pressures of 27 mm Hg or greater and evidence of optic nerve damage in both eyes will be eligible for enrollment. Patients will be followed for a minimum of two years in order to collect information on pressure levels over the course of the trial and to provide comparative data on the rate of visual field loss and increased optic nerve cupping. Treatment groups will be compared at the end of the two years with regard to the amount of medical treatment needed to control the intraocular pressure and/or control glaucomatous nerve damage. The eye to be lasered will be randomly selected. The procedure will consist of 96 burns delivered to the anterior pigmented portion of the trabecular meshwork, avoiding the posterior portion of the meshwork and scleral spur. The burns will be delivered at an intensity sufficient to cause blanching of the meshwork just at the threshold of bubble formation (700-1200 mW). The fellow eye will be assigned to medical therapy and placed on a single topical medication. Eyes requiring added treatment over and above the initial treatment will have subsequent topical medication added in a step-wise fashion according to a protocol. The trial will involve 6 clinical centers, a data coordinating center, a disc stereophoto reading center, and visual field reading center.